Red Hat System Administration I

[student@workstation ~]$ date
Thu Jan 22 10:13:04 PDT 2019

Use the +%r argument with the date command to display the current time in 12-hour clock time.

[student@workstation ~]$ date +%r
10:14:07 AM

Use the file command to determine its file type.

[student@workstation ~]$ file zcat
zcat: POSIX shell script, ASCII text executable

The wc command can be used to display the number of lines, words, and bytes in the zcat script. Instead of retyping the file name, use the Bash history shortcut Esc+. (the keys Esc and . pressed at the same time) to reuse the argument from the previous command.

[student@workstation ~]$ wc Esc+.
[student@workstation ~]$ wc zcat
  51  299 1983 zcat

The head command displays the beginning of the file. Try using the Esc+. shortcut again.

[student@workstation ~]$ head Esc+.
[student@workstation ~]$ head zcat
#!/bin/sh
# Uncompress files to standard output.

# Copyright (C) 2007, 2010-2018 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.

Use the tail command to display the last 10 lines of the zcat file.

[student@workstation ~]$ tail Esc+.
[student@workstation ~]$ tail zcat
With no FILE, or when FILE is -, read standard input.

Report bugs to <bug-gzip@gnu.org>."

case $1 in
--help)    printf '%s\n' "$usage"   || exit 1;;
--version) printf '%s\n' "$version" || exit 1;;
esac

exec gzip -cd "$@"

Repeat the previous command exactly. Either press the UpArrow key once to scroll back through the command history one command and then press Enter (uses two keystrokes), or enter the shortcut command !! and then press Enter (uses three keystrokes) to run the most recent command in the command history . (Try both.)

[student@workstation]$ !!
tail zcat
With no FILE, or when FILE is -, read standard input.

Report bugs to <bug-gzip@gnu.org>."

case $1 in
--help)    printf '%s\n' "$usage"   || exit 1;;
--version) printf '%s\n' "$version" || exit 1;;
esac

exec gzip -cd "$@"

UpArrow displays the previous command. Ctrl+A makes the cursor jump to the beginning of the line. Ctrl+RightArrow jumps to the next word, then add the -n 20 option and hit Enter to execute the command.

[student@workstation ~]$ tail -n 20 zcat
  -l, --list        list compressed file contents
  -q, --quiet       suppress all warnings
  -r, --recursive   operate recursively on directories
  -S, --suffix=SUF  use suffix SUF on compressed files
      --synchronous synchronous output (safer if system crashes, but slower)
  -t, --test        test compressed file integrity
  -v, --verbose     verbose mode
      --help        display this help and exit
      --version     display version information and exit

With no FILE, or when FILE is -, read standard input.

Report bugs to <bug-gzip@gnu.org>."

case $1 in
--help)    printf '%s\n' "$usage"   || exit 1; exit;;
--version) printf '%s\n' "$version" || exit 1; exit;;
esac

exec gzip -cd "$@"

Use the history command to display the list of previous commands and to identify the specific date command to be executed. Use !number to run the command, where number is the command number to use from the output of the history command.

Note that your shell history may be different from the following example. Determine the command number to use based on the output of your own history command.

[student@workstation ~]$ history
1   date
2   date +%r
3   file zcat
4   wc zcat
5   head zcat
6   tail zcat
7   tail -n 20 zcat
8   history
[student@workstation ~]$ !2
date +%r
10:49:56 AM